1. Field of the Invention
The present invention relates to a liquid crystal display device and a defect correction method therefor. More specifically, the present invention relates to a liquid crystal display device in which each pixel electrode includes a plurality of sub-pixel electrodes, and a defect correction method therefor.
2. Related Art and Other Considerations
Liquid crystal display devices, being slim in shape and having a small power consumption, have been widely used in various applications, including OA apparatuses such as word processors and personal computers, personal digital assistances such as electronic organizers, and monitors of camcorders.
Unlike a CRT (cathode ray tube) and an EL (electroluminescence) device, a liquid crystal display device itself does not emit light. Therefore, a liquid crystal display device typically displays an image by using light from an illumination device having a fluorescent tube therein (called a xe2x80x9cbacklightxe2x80x9d) which is arranged on the back side of the liquid crystal display device (this type of liquid crystal display device is called a xe2x80x9ctransmission type liquid crystal display devicexe2x80x9d). The backlight typically consumes more than 50% of the total power consumed by the liquid crystal display device. Therefore, apparatuses which are used outdoors and those which are always carried around by the user employ another type of liquid crystal display device (called a xe2x80x9creflection type liquid crystal display devicexe2x80x9d) which is provided with a reflection plate instead of a backlight so as to display an image using the ambient light.
However, a reflection type liquid crystal display device has a very poor visibility when the ambient light is dark, while a transmission type liquid crystal display device has a poor visibility when the ambient light is very bright, e.g., under a clear sky, etc. In view of this, transmission-reflection type liquid crystal display devices (hereinafter, referred to as xe2x80x9ctwo-way liquid crystal display devicesxe2x80x9d) have been developed. A two-way liquid crystal display device includes a reflection electrode made of a light-reflecting material and a transparent electrode made of a light-transmitting material which are provided in the form of a single panel. A two-way liquid crystal display device can operate as a transmission type liquid crystal display device, when the ambient light is dark, displaying an image using light from a backlight which is transmitted through the transparent electrode, and can also operate as a reflection type liquid crystal display device, when the ambient light is bright, displaying an image using the ambient light reflected by the reflection electrode.
A two-way liquid crystal display device has a reduced power consumption as compared to a conventional transmission type liquid crystal display device because it does not use the backlight when the ambient light is bright. A two-way liquid crystal display device does not have the problem of being unable to obtain a sufficiently bright display when the ambient light is dark as in a conventional reflection type liquid crystal display device because it can display an image using the backlight when the ambient light is dark. In addition, a two-way liquid crystal display device, while operating as a transmission type display device, suppresses the undesirable reflection of the ambient light, e.g., light from a fluorescent lamp (which may be used for the display in a reflection mode), on the display surface, thereby improving the display quality of a transmission type liquid crystal display device.
However, the inventors of the present invention have found that when a display defect occurs in a two-way liquid crystal display device due to a short-circuit between a pixel electrode and the counter electrode or between adjacent pixel electrodes, the display defect cannot effectively be corrected with a conventional structure and a conventional correction method.
In a two-way liquid crystal display device having pixel electrodes each including a transparent electrode provided under an interlayer insulative film and a reflection electrode provided over the interlayer insulative film, a short-circuit caused by electrically conductive foreign matter often occurs between a reflection electrode and the counter electrode or between adjacent reflection electrodes.
When a display defect occurs due to such a short-circuit, if only the reflection electrode can be electrically disconnected, the transmission region of the defective pixel can still normally display an image because a predetermined voltage can still be applied to the transparent electrode. Thus, it is possible to correct the display defect without sacrificing the whole of the defective pixel.
However, with the conventional two-way liquid crystal display device structure and the conventional defect correction method, it is difficult to electrically disconnect only the reflection electrode, selectively, while maintaining the normal electrical connection of the transparent electrode.
This problem is not exclusively inherent to a two-way liquid crystal display device, but is common among various liquid crystal display devices in which each pixel electrode includes two or more sub-pixel electrodes (also called xe2x80x9cdivided pixel electrodesxe2x80x9d) which have respectively different distances from the counter electrode (interelectrode gaps).
In view of the above-mentioned conventional problem, the present invention has been devised for the purpose of realizing a liquid crystal display device in which each pixel electrode includes a plurality of sub-pixel electrodes and for which it is easy to correct a short-circuit defect, and realizing a method for correcting such a defect.
A liquid crystal display device of the present invention includes: a first substrate; a second substrate; and a liquid crystal layer provided between the first substrate and the second substrate, the first substrate including a plurality of switching elements and a plurality of pixel electrodes electrically connected to the plurality of switching elements, respectively, and the second substrate including a counter substrate opposing the plurality of pixel electrodes via the liquid crystal layer, wherein: each of the plurality of pixel electrodes includes a first sub-pixel electrode and a second sub-pixel electrode which are electrically connected to one of the switching elements, a distance between the first sub-pixel electrode and the counter electrode being greater than a distance between the second sub-pixel electrode and the counter electrode; and the second sub-pixel electrode is electrically connected to the switching element via a connection line provided separately from a path which electrically connects the first sub-pixel electrode to the switching element. Thus, the above-described object is achieved.
The first sub-pixel electrode may be a transparent electrode, and the second sub-pixel electrode may be a reflection electrode.
The liquid crystal display device may further include an interlayer insulative film provided over the plurality of switching elements, wherein the transparent electrode is provided under the interlayer insulative film, and the reflection electrode is provided over the interlayer insulative film.
The connection line may be provided from a same conductive layer as the transparent electrode, and the reflection electrode may be connected to the connection line via a contact hole provided in the interlayer insulative film.
The contact hole may be provided in a region where light from a first substrate side is not transmitted.
Preferably, the connection line has a second region whose line width is smaller than that of a first region corresponding to the contact hole.
The second region of the connection line may be provided in a region where light coming from a first substrate side is transmitted.
The reflection electrode may not be provided over the second region of the connection line.
The second substrate may include a light-blocking layer in a region opposing the second region of the connection line.
A method of the present invention is a method for correcting a defect in any of the above-described liquid crystal display devices, including the steps of: identifying a pixel electrode, among the plurality of pixel electrodes, in which a short-circuit defect via the second sub-pixel electrode has occurred; and electrically disconnecting the second sub-pixel electrode of the identified pixel electrode from the switching element by cutting off the connection line while maintaining the electrical connection between the first sub-pixel electrode of the identified pixel electrode and the switching element. Thus, the above-described object is achieved.
Preferably, where two adjacent pixel electrodes among the plurality of pixel electrodes are short-circuited with each other via the second sub-pixel electrode of one of the two adjacent pixel electrodes, the second sub-pixel electrode of one of the two adjacent pixel electrodes to which a write operation is performed first during a same frame is electrically disconnected from the switching element.